158 RECORDS. 



We may conclude, therefore, that plates measured by the reseau 

 method and without it give identical results within a very narrow 

 margin ; nor does irregular distortion of the film appear to have 

 affected appreciably the measures made without the reseau. 



Mr. Trowbridge's paper was a continuation of the results 

 read before the Academy at the meeting on March 3, 1902. 



S. A. Mitchell, 



Secretary. 

 SECTION OF BIOLOGY. 



January 12, 1903. 



Section met at 8:15 P. M., Professor Bashford Dean presid- 

 ing. The minutes of the last meeting of Section were read and 

 approved. 



The following program was then offered : 



Gary N. Calkins, Protoplasmic Old Age. 



A. G. Mayer, The Dry Tortugas as a Biological Station 



FOR Research. 



Summary of Papers. 



The paper by Dr. Calkins was based upon his studies of 

 Paraviceciwn, individuals of which were isolated in February, 

 1 901, and their descendants kept under observation for 23 

 months when the series ended by the death of all individuals of 

 the 742d generation. It was pointed out that in the course of 

 the 742 generations there were four well-marked periods of 

 depression or "old age"; and the accompanying cytological 

 changes, reproductive conditions, and the effects of stimuli 

 were described and discussed. 



The paper by Dr. Mayer showed the advantages of the Dry 

 Tortugas for biological research. With the aid of lantern illus- 

 trations. Dr. Mayer described the favorable conditions with 

 reference to geographical position in relation to ocean currents, 

 the topography, and the nature of the fauna and flora. The 

 complete paper has been prepared for publication in Science. 



Dr. Piffard exhibited a set of X-ray photographs of gastro- 

 pod shells, designed to obviate the sectioning of rare specimens. 



M. A. Bigelow, 



Secretary. 



